A video encoder compresses video information so that more information can be sent over a given bandwidth. The compressed signal may then be transmitted to a receiver that decodes or decompresses the signal prior to display.
High Efficient Video Coding (HEVC) is a new video compression standard planned to be finalized by the end 2012. It is currently under development by the Joint Collaborative Team on Video Coding (JCT-VC) formed by ISO/IEC Moving Picture Experts Group (MPEG) and ITU-T Video Coding Experts Group (VCEG). Similar with previous video coding standards, HEVC consists of basic modules such as intra/inter prediction, transform, quantization and in-loop filtering and entropy coding.
HEVC defines Coding Units (CUs), which are used to sub-partition a picture into rectangular blocks with variable size. The Largest coding unit (LCU) can be a 64×64 block, a 32×32 block or a 16×16 block. A LCU can be encoded directly or be divided into 4 Coding Unit (CU) for next level encoding. For a CU in one level, it can be encoded directly or be further divided into next level for encoding. The smallest CU is 8×8. Within each LCU, a quadtree based splitting scheme may be used to specify the coding unit partition pattern.
In addition, Prediction Units (PUs) and Transform Units (TUs) are also defined by HEVC to specify how to divide a coding unit to do the prediction and transform, respectively. The PU segmentation depends on the coding unit coding mode. When intra coded, a coding unit with size equal to 2N×2N can be predicted in one 2N×2N PU or in four N×N PUs. When inter coded, a 2N×2N coding unit can be predicted in one 2N×2N PU, or two 2N×N PUs, or two N×2N PUs, or one 0.5N×2N PU and one 1.5N×2N PU, or one 1.5N×2N PU and one 0.5N×2N PU, or one 2N×0.5N PU and one 2N×1.5N PU, or one 2N×1.5N PU and one 2N×0.5N PU, or four N×N PUs.
The TU partition may also be quadtree splitting based. For example, a series of block transform cores may be define in HEVC, which can be 32×32 blocks, 16×16 blocks, 8×8 blocks, and/or 4×4 blocks. After the intra or inter prediction, the transform applies to the residual blocks to generate coefficients. After that, the coefficients may be quantized, scanned into one-dimensional order and finally Context-adaptive binary arithmetic coding (CABAC) coded.